ioprio: move io priority from task_struct to io_context

This is where it belongs and then it doesn't take up space for a
process that doesn't do IO.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

9 files changed, 178 insertions, 122 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 13553e015d72..533af75329e6 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -199,7 +199,7 @@ CFQ_CFQQ_FNS(sync);
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
-                                       struct task_struct *, gfp_t);
+                                       struct io_context *, gfp_t);
 static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
                                                 struct io_context *);
 
@@ -1273,7 +1273,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
         return cic;
 }
 
-static void cfq_init_prio_data(struct cfq_queue *cfqq)
+static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 {
         struct task_struct *tsk = current;
         int ioprio_class;
@@ -1281,7 +1281,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
         if (!cfq_cfqq_prio_changed(cfqq))
                 return;
 
-        ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
+        ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
         switch (ioprio_class) {
                 default:
                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
@@ -1293,11 +1293,11 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
                         break;
                 case IOPRIO_CLASS_RT:
-                        cfqq->ioprio = task_ioprio(tsk);
+                        cfqq->ioprio = task_ioprio(ioc);
                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
                         break;
                 case IOPRIO_CLASS_BE:
-                        cfqq->ioprio = task_ioprio(tsk);
+                        cfqq->ioprio = task_ioprio(ioc);
                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
                         break;
                 case IOPRIO_CLASS_IDLE:
@@ -1330,8 +1330,7 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
         cfqq = cic->cfqq[ASYNC];
         if (cfqq) {
                 struct cfq_queue *new_cfqq;
-                new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
-                                         GFP_ATOMIC);
+                new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
                 if (new_cfqq) {
                         cic->cfqq[ASYNC] = new_cfqq;
                         cfq_put_queue(cfqq);
@@ -1363,13 +1362,13 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
 
 static struct cfq_queue *
 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
-                     struct task_struct *tsk, gfp_t gfp_mask)
+                     struct io_context *ioc, gfp_t gfp_mask)
 {
         struct cfq_queue *cfqq, *new_cfqq = NULL;
         struct cfq_io_context *cic;
 
 retry:
-        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        cic = cfq_cic_rb_lookup(cfqd, ioc);
         /* cic always exists here */
         cfqq = cic_to_cfqq(cic, is_sync);
 
@@ -1412,7 +1411,7 @@ retry:
                 cfq_mark_cfqq_prio_changed(cfqq);
                 cfq_mark_cfqq_queue_new(cfqq);
 
-                cfq_init_prio_data(cfqq);
+                cfq_init_prio_data(cfqq, ioc);
         }
 
         if (new_cfqq)
@@ -1439,11 +1438,11 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
               gfp_t gfp_mask)
 {
-        const int ioprio = task_ioprio(tsk);
-        const int ioprio_class = task_ioprio_class(tsk);
+        const int ioprio = task_ioprio(ioc);
+        const int ioprio_class = task_ioprio_class(ioc);
         struct cfq_queue **async_cfqq = NULL;
         struct cfq_queue *cfqq = NULL;
 
@@ -1453,7 +1452,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
         }
 
         if (!cfqq) {
-                cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
+                cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
                 if (!cfqq)
                         return NULL;
         }
@@ -1793,7 +1792,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 
-        cfq_init_prio_data(cfqq);
+        cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
 
         cfq_add_rq_rb(rq);
 
@@ -1900,7 +1899,7 @@ static int cfq_may_queue(struct request_queue *q, int rw)
 
         cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
         if (cfqq) {
-                cfq_init_prio_data(cfqq);
+                cfq_init_prio_data(cfqq, cic->ioc);
                 cfq_prio_boost(cfqq);
 
                 return __cfq_may_queue(cfqq);
@@ -1938,7 +1937,6 @@ static int
 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
-        struct task_struct *tsk = current;
         struct cfq_io_context *cic;
         const int rw = rq_data_dir(rq);
         const int is_sync = rq_is_sync(rq);
@@ -1956,7 +1954,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
         cfqq = cic_to_cfqq(cic, is_sync);
         if (!cfqq) {
-                cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
+                cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
 
                 if (!cfqq)
                         goto queue_fail;
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3d0422f48453..b9bb02e845cd 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3904,6 +3904,26 @@ void exit_io_context(void)
         put_io_context(ioc);
 }
 
+struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
+{
+        struct io_context *ret;
+
+        ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+        if (ret) {
+                atomic_set(&ret->refcount, 1);
+                ret->task = current;
+                ret->ioprio_changed = 0;
+                ret->ioprio = 0;
+                ret->last_waited = jiffies; /* doesn't matter... */
+                ret->nr_batch_requests = 0; /* because this is 0 */
+                ret->aic = NULL;
+                ret->cic_root.rb_node = NULL;
+                ret->ioc_data = NULL;
+        }
+
+        return ret;
+}
+
 /*
  * If the current task has no IO context then create one and initialise it.
  * Otherwise, return its existing IO context.
@@ -3921,16 +3941,8 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
         if (likely(ret))
                 return ret;
 
-        ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+        ret = alloc_io_context(gfp_flags, node);
         if (ret) {
-                atomic_set(&ret->refcount, 1);
-                ret->task = current;
-                ret->ioprio_changed = 0;
-                ret->last_waited = jiffies; /* doesn't matter... */
-                ret->nr_batch_requests = 0; /* because this is 0 */
-                ret->aic = NULL;
-                ret->cic_root.rb_node = NULL;
-                ret->ioc_data = NULL;
                 /* make sure set_task_ioprio() sees the settings above */
                 smp_wmb();
                 tsk->io_context = ret;
diff --git a/fs/ioprio.c b/fs/ioprio.c
index e4e01bc7f338..a7600401ecf7 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -41,18 +41,29 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
                 return err;
 
         task_lock(task);
+        do {
+                ioc = task->io_context;
+                /* see wmb() in current_io_context() */
+                smp_read_barrier_depends();
+                if (ioc)
+                        break;
 
-        task->ioprio = ioprio;
-
-        ioc = task->io_context;
-        /* see wmb() in current_io_context() */
-        smp_read_barrier_depends();
+                ioc = alloc_io_context(GFP_ATOMIC, -1);
+                if (!ioc) {
+                        err = -ENOMEM;
+                        break;
+                }
+                task->io_context = ioc;
+                ioc->task = task;
+        } while (1);
 
-        if (ioc)
+        if (!err) {
+                ioc->ioprio = ioprio;
                 ioc->ioprio_changed = 1;
+        }
 
         task_unlock(task);
-        return 0;
+        return err;
 }
 
 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
@@ -148,7 +159,9 @@ static int get_task_ioprio(struct task_struct *p)
         ret = security_task_getioprio(p);
         if (ret)
                 goto out;
-        ret = p->ioprio;
+        ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
+        if (p->io_context)
+                ret = p->io_context->ioprio;
 out:
         return ret;
 }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 49b7a4c31a6d..510a18ba1ec5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -34,83 +34,10 @@ struct sg_io_hdr;
 #define BLKDEV_MIN_RQ   4
 #define BLKDEV_MAX_RQ   128     /* Default maximum */
 
-/*
- * This is the per-process anticipatory I/O scheduler state.
- */
-struct as_io_context {
-        spinlock_t lock;
-
-        void (*dtor)(struct as_io_context *aic); /* destructor */
-        void (*exit)(struct as_io_context *aic); /* called on task exit */
-
-        unsigned long state;
-        atomic_t nr_queued; /* queued reads & sync writes */
-        atomic_t nr_dispatched; /* number of requests gone to the drivers */
-
-        /* IO History tracking */
-        /* Thinktime */
-        unsigned long last_end_request;
-        unsigned long ttime_total;
-        unsigned long ttime_samples;
-        unsigned long ttime_mean;
-        /* Layout pattern */
-        unsigned int seek_samples;
-        sector_t last_request_pos;
-        u64 seek_total;
-        sector_t seek_mean;
-};
-
-struct cfq_queue;
-struct cfq_io_context {
-        struct rb_node rb_node;
-        void *key;
-
-        struct cfq_queue *cfqq[2];
-
-        struct io_context *ioc;
-
-        unsigned long last_end_request;
-        sector_t last_request_pos;
-
-        unsigned long ttime_total;
-        unsigned long ttime_samples;
-        unsigned long ttime_mean;
-
-        unsigned int seek_samples;
-        u64 seek_total;
-        sector_t seek_mean;
-
-        struct list_head queue_list;
-
-        void (*dtor)(struct io_context *); /* destructor */
-        void (*exit)(struct io_context *); /* called on task exit */
-};
-
-/*
- * This is the per-process I/O subsystem state.  It is refcounted and
- * kmalloc'ed. Currently all fields are modified in process io context
- * (apart from the atomic refcount), so require no locking.
- */
-struct io_context {
-        atomic_t refcount;
-        struct task_struct *task;
-
-        unsigned int ioprio_changed;
-
-        /*
-         * For request batching
-         */
-        unsigned long last_waited; /* Time last woken after wait for request */
-        int nr_batch_requests;     /* Number of requests left in the batch */
-
-        struct as_io_context *aic;
-        struct rb_root cic_root;
-        void *ioc_data;
-};
-
 void put_io_context(struct io_context *ioc);
 void exit_io_context(void);
 struct io_context *get_io_context(gfp_t gfp_flags, int node);
+struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
 void copy_io_context(struct io_context **pdst, struct io_context **psrc);
 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);
 
@@ -894,6 +821,12 @@ static inline void exit_io_context(void)
 {
 }
 
+static inline int put_io_context(struct io_context *ioc)
+{
+        return 1;
+}
+
+
 #endif /* CONFIG_BLOCK */
 
 #endif
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 796019b22b6f..e6b3f7080679 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -137,7 +137,6 @@ extern struct group_info init_groups;
                 .time_slice     = HZ,                                   \
                 .nr_cpus_allowed = NR_CPUS,                             \
         },                                                              \
-        .ioprio         = 0,                                            \
         .tasks          = LIST_HEAD_INIT(tsk.tasks),                    \
         .ptrace_children= LIST_HEAD_INIT(tsk.ptrace_children),          \
         .ptrace_list    = LIST_HEAD_INIT(tsk.ptrace_list),              \
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
new file mode 100644
index 000000000000..186807ea62e2
--- /dev/null
+++ b/include/linux/iocontext.h
@@ -0,0 +1,79 @@
+#ifndef IOCONTEXT_H
+#define IOCONTEXT_H
+
+/*
+ * This is the per-process anticipatory I/O scheduler state.
+ */
+struct as_io_context {
+        spinlock_t lock;
+
+        void (*dtor)(struct as_io_context *aic); /* destructor */
+        void (*exit)(struct as_io_context *aic); /* called on task exit */
+
+        unsigned long state;
+        atomic_t nr_queued; /* queued reads & sync writes */
+        atomic_t nr_dispatched; /* number of requests gone to the drivers */
+
+        /* IO History tracking */
+        /* Thinktime */
+        unsigned long last_end_request;
+        unsigned long ttime_total;
+        unsigned long ttime_samples;
+        unsigned long ttime_mean;
+        /* Layout pattern */
+        unsigned int seek_samples;
+        sector_t last_request_pos;
+        u64 seek_total;
+        sector_t seek_mean;
+};
+
+struct cfq_queue;
+struct cfq_io_context {
+        struct rb_node rb_node;
+        void *key;
+
+        struct cfq_queue *cfqq[2];
+
+        struct io_context *ioc;
+
+        unsigned long last_end_request;
+        sector_t last_request_pos;
+
+        unsigned long ttime_total;
+        unsigned long ttime_samples;
+        unsigned long ttime_mean;
+
+        unsigned int seek_samples;
+        u64 seek_total;
+        sector_t seek_mean;
+
+        struct list_head queue_list;
+
+        void (*dtor)(struct io_context *); /* destructor */
+        void (*exit)(struct io_context *); /* called on task exit */
+};
+
+/*
+ * This is the per-process I/O subsystem state.  It is refcounted and
+ * kmalloc'ed. Currently all fields are modified in process io context
+ * (apart from the atomic refcount), so require no locking.
+ */
+struct io_context {
+        atomic_t refcount;
+        struct task_struct *task;
+
+        unsigned short ioprio;
+        unsigned short ioprio_changed;
+
+        /*
+         * For request batching
+         */
+        unsigned long last_waited; /* Time last woken after wait for request */
+        int nr_batch_requests;     /* Number of requests left in the batch */
+
+        struct as_io_context *aic;
+        struct rb_root cic_root;
+        void *ioc_data;
+};
+
+#endif
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index baf29387cab4..2a3bb1bb7433 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -2,6 +2,7 @@
 #define IOPRIO_H
 
 #include <linux/sched.h>
+#include <linux/iocontext.h>
 
 /*
  * Gives us 8 prio classes with 13-bits of data for each class
@@ -45,18 +46,18 @@ enum {
  * the cpu scheduler nice value to an io priority
  */
 #define IOPRIO_NORM     (4)
-static inline int task_ioprio(struct task_struct *task)
+static inline int task_ioprio(struct io_context *ioc)
 {
-        if (ioprio_valid(task->ioprio))
-                return IOPRIO_PRIO_DATA(task->ioprio);
+        if (ioprio_valid(ioc->ioprio))
+                return IOPRIO_PRIO_DATA(ioc->ioprio);
 
         return IOPRIO_NORM;
 }
 
-static inline int task_ioprio_class(struct task_struct *task)
+static inline int task_ioprio_class(struct io_context *ioc)
 {
-        if (ioprio_valid(task->ioprio))
-                return IOPRIO_PRIO_CLASS(task->ioprio);
+        if (ioprio_valid(ioc->ioprio))
+                return IOPRIO_PRIO_CLASS(ioc->ioprio);
 
         return IOPRIO_CLASS_BE;
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index df5b24ee80b3..80837e7d527e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -975,7 +975,6 @@ struct task_struct {
         struct hlist_head preempt_notifiers;
 #endif
 
-        unsigned short ioprio;
         /*
          * fpu_counter contains the number of consecutive context switches
          * that the FPU is used. If this is over a threshold, the lazy fpu
diff --git a/kernel/fork.c b/kernel/fork.c
index 39d22b3357de..2a86c9dff744 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -51,6 +51,7 @@
 #include <linux/random.h>
 #include <linux/tty.h>
 #include <linux/proc_fs.h>
+#include <linux/blkdev.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -791,6 +792,26 @@ out:
         return error;
 }
 
+static int copy_io(struct task_struct *tsk)
+{
+#ifdef CONFIG_BLOCK
+        struct io_context *ioc = current->io_context;
+
+        if (!ioc)
+                return 0;
+
+        if (ioprio_valid(ioc->ioprio)) {
+                tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
+                if (unlikely(!tsk->io_context))
+                        return -ENOMEM;
+
+                tsk->io_context->task = tsk;
+                tsk->io_context->ioprio = ioc->ioprio;
+        }
+#endif
+        return 0;
+}
+
 /*
  *      Helper to unshare the files of the current task.
  *      We don't want to expose copy_files internals to
@@ -1156,15 +1177,17 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                 goto bad_fork_cleanup_mm;
         if ((retval = copy_namespaces(clone_flags, p)))
                 goto bad_fork_cleanup_keys;
+        if ((retval = copy_io(p)))
+                goto bad_fork_cleanup_namespaces;
         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
         if (retval)
-                goto bad_fork_cleanup_namespaces;
+                goto bad_fork_cleanup_io;
 
         if (pid != &init_struct_pid) {
                 retval = -ENOMEM;
                 pid = alloc_pid(task_active_pid_ns(p));
                 if (!pid)
-                        goto bad_fork_cleanup_namespaces;
+                        goto bad_fork_cleanup_io;
 
                 if (clone_flags & CLONE_NEWPID) {
                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
@@ -1234,9 +1257,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         /* Need tasklist lock for parent etc handling! */
         write_lock_irq(&tasklist_lock);
 
-        /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
-        p->ioprio = current->ioprio;
-
         /*
          * The task hasn't been attached yet, so its cpus_allowed mask will
          * not be changed, nor will its assigned CPU.
@@ -1328,6 +1348,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 bad_fork_free_pid:
         if (pid != &init_struct_pid)
                 free_pid(pid);
+bad_fork_cleanup_io:
+        put_io_context(p->io_context);
 bad_fork_cleanup_namespaces:
         exit_task_namespaces(p);
 bad_fork_cleanup_keys: